1. FIELD OF THE INVENTION:
The invention relates to a device for measuring the amount of tension applied to a tensile force transmitting element, such as a flexible cable, chain or band.
2. DESCRIPTION OF THE PRIOR ART:
There are many industrial applications where it is desirable to know with reasonable accuracy the amount of tension application to a cable, chain or band, or similar tensile force transmitting element. In this manner, it is assured that the tensile transmitting element will not be subjected to excess force resulting in its breakage or, equally important, that sufficient tension exists in the tension transmitting element to enable it to perform a particular function, for example, a chain holding a load on a truck bed.
Numerous patents have been issued on devices for measuring tension in cables. A large group of such patents, represented by the disclosures of U.S. Pat. No. 1,722,036 to BLY; U.S. Pat. No. 3,174,334 to McKERNAN;and U.S. Pat. No. 3,653,258 to KING, disclose a tension measuring device which is applied to a stressed cable, and an actuating member imposes a lateral force on the stressed cable. The amount of deflection of the stressed cable in response to the lateral force is measured and this measurement provides an indication of the degree of tension in the stressed cable.
This type of device is particularly applicable to measuring stress already existing in a stressed cable, i.e., the measuring apparatus can be applied to the stressed cable and a measurement taken without the stress being removed from the cable.
There are numerous industrial applications wherein the opportunity exists for applying the stress measuring device to the cable prior to the application of substantial stress thereto. This technique permits a substantial degree of simplification of the measuring apparatus. For example, U.S. Pat. No. 3,868,662 to RUSSELL discloses an E-shaped support through which an unstressed band is inserted. The application of stress to the band causes a longitudinal deformation of the E-shaped support and the extent of this deformation is either indicated by the closing of a switch carried by the support or visually by an indicator bar mounted on the support and cooperating with another element of the support for indicating the degree of support deformation.
In any event, the prior art devices are characterized by being relatively complicated, involving a number of parts, some of which are relatively movable, and being expensive to manufacture. The need exists for an inexpensive, rugged device suitable for use in adverse environmental conditions, such as well drilling rigs, which may be applied to a wide range of sizes of cables, chains or the like, and will nevertheless provide a reliable indication of the amount of tension applied to the cable, chain or similar tensile force transmitting element.